Abstract

We evaluated the biological characteristics of lung cancer by measuring their contents of human 28 kDa vitamin D-dependent calcium binding protein (calbindin-D). Calbindin-D concentrations were determined in tumor tissue and normal lung tissue extracts from patients with lung cancer by enzyme immunoassay. The percentage of high calbindin-D containing tissues in small cell lung cancer (SCLC) was significantly higher than that in non-small cell lung cancer (NSCLC) and the calbindin-D concentration was low in normal lung extracts. In addition, most of the NSCLC which had a significantly high level of calbindin-D were at the advanced cancer stage with lymph node metastasis. Calbindin-D concentrations were also determined in lung cancer cell lines. The percentage of high calbindin-D containing cell lines was high in classic type SCLC, followed in order by variant type SCLC and NSCLC. In addition, in order to examine the usefulness of calbindin-D as a marker of neuroendocrine properties of lung cancer, we compared the sensitivity and specificity of calbindin-D for distinguishing classic from variant type SCLC with neuron-specific enolase (NSE) and aromatic L-amino acid decarboxylase (AADC) by relative operating characteristic curves. The diagnostic accuracy of AADC was the highest of the three and that of calbindin-D was as high as that of NSE. These findings suggest calbindin-D to be related to the neuroendocrine properties of lung cancer.